In high-voltage electrical systems, a fault condition can lead to serious damage of the equipment very quickly. It is accordingly very important to actuate a circuit breaker or other protector device as quickly as possible when a fault condition is detected. It is well known to actuate such protective devices by chemical means. Systems employing such chemical actuators are shown in the following copending applications: Ser. No. 887,172, filed Mar. 16, 1978, now U.S. Pat. No. 4,224,491, Peter J. Kroon, for a CHEMICALLY ACTIVATED SWITCH; Ser. No. 889,491, filed Mar. 22, 1978, now U.S. Pat. No. 4,250,365, Lorne D. McConnell, for a CURRENT INTERRUPTOR FOR FAULT CURRENT LIMITER AND METHOD; and Ser. No. 899,539, filed Apr. 24, 1978, Rolf Dethlefson, for EXPLOSIVELY ACTIVATED FAULT CURRENT LIMITER, which issued as U.S. Pat. No. 4,176,385 on Nov. 17, 1979. All of the foregoing are assigned to the Electric Power Research Institute. It is known, for example, to power the open stroke of a circuit breaker by a chemical explosive charge. The charge is typically detonated by electrical means, for example by a power pulse from a capacitor discharge circuit. The capacitor discharge circuit must be located near the switch-actuator assembly and must, in a high-voltage power system, be kept at line potential. The capacitor discharge circuit is highly sensitive to high-level power system noise, against which it must accordingly be heavily shielded.